Former auditors to iSoft, the NHS software supplier which secured a high court gagging order against a Guardian investigation into its accounts six years ago, are to be the subject of a disciplinary hearing following an investigation by the Accountancy & Actuarial Discipline Board.

The professional regulatory body has filed a complaint against RSM Robson Rhodes – which has since merged with rival Grant Thornton – and against Glyn Williams, who led the iSoft audit team. The allegations, to be contested in front of an independent tribunal, relate to financial statements between 2003 and 2005.

The action comes after a tribunal finding earlier this year that iSoft's financial controller Ian Storey repeatedly provided false and misleading information to auditors in relation to a purported contract. He was banned from practising as an accountant for eight years and fined £20,000.

Meanwhile an AADB investigation into the conduct of iSoft's past executives and non-executives remains live, but progress has been suspended as co-founder Patrick Cryne and three other former executives are facing a criminal trial over charges they conspired to make misleading statements to the market over the software group's financial performance.

The latest AADB complaint focuses on allegations that Robson Rhodes was involved in improper revenue recognition on long-term contracts, as well as alleged balance sheet and goodwill accounting abuses. Robson Rhodes has promised to contest the AADB's claims. Williams remains a partner with Grant Thornton, working in its Manchester office.

Irregularities at iSoft were discovered in 2006 by Deloitte, which took over from RSM Robson Rhodes in July 2005. Months later the government helped broker a rescue takeover of iSoft by much smaller Australian group IBA Health – a business that later changed its name to iSoft. The group's patient administration system software was to be a central plank of Labour's £12.7bn NHS IT overhaul. Development setbacks and software failures have been blamed for years of delays and cost overruns.

In 2004 an investigation by the Guardian raised serious concerns about a possible mismatch between iSoft's cash position and its reported revenues. But the findings could not be reported because the courts granted iSoft a gagging order over the Guardian and its reporter Ian Griffiths. The order was lifted in November 2006.

When presented with questions over iSoft's accounting practices in 2004, Lord Jones of Birmingham, UK business ambassador and former trade minister, accused the Guardian of "serious and unfounded insinuations of impropriety". He said he was "satisfied that the company has followed best practice" and said he had thoroughly investigated allegations put by the newspaper.

He has since said he welcomed an investigation by the FSA into the affairs of iSoft, adding: "I will be making no further comment."